Heat-treating gear



Sept. 12, 1950 s, DENNEEN ETAL 2,521,699

HEAT-TREATING GEAR Original Filed March 23, 1942 Patented Sept. 12, 1950 UNITED STATES PATENT OFFICE, I .2,5.21,e99"" Dunn, Shaker Heights, Ohio, assignors to The Ohio Crankshaft Company, Cleveland, Ohio,

a corporation of Ohio Original application March 23, 1942, SerialNo. 435,912. Divided and this application March 5, 1946, Serial No. 652,091

4 Claims. (Cl. 219-13) 1 This application is a division of our copending application Ser. No. 435,912 for Heat Treating of Gear Teeth, filed March 23, 1942, now Patent Number 2,398,085, dated April 9, 1946, and is concerned chiefly with the apparatus of Figs. 3,4,

and 5 of that application and with modifications of that apparatus, all of which disclose means and method for heat treating the surface zones of ears and similar articles.

In the heat treatment of metals generally and in the hardening of ferrous metals in particular,

there have been no teachings which would enable those skilled in the art to produce hardened zones of metal of predetermined characteristics as to depth and general contour on articles having abrupt or irregular changes in surface form by the use of electric heat. Surface hardening processes used heretofore were not adapted to the hardening of such surfaces as the contacting surfaces of gear teeth or splines, the side walls of sliding keys and keyways, the rifled interiors of gun bores, and many other similar surfaces. In the hardening of such surfaces as those above enumerated, it is often important that adjacent surfaces as well as the core or metal under the surface, be kept softer in order that it be sufficiently ductile to resist fractures due to shock, vibrations and other causes. For instance, in a gear tooth, the addendum surfaces should be hard in order to resist the abrasion of sliding and rolling contact of other tooth surfaces, while the metal in the dedendum' and at the root of the tooth which does not contact with any wearing or abrasive element, but which is submitted to heavy bending stresses due to the cantilever construction of gear teeth, should remain strong and comparatively ductile to prevent breakage or the formation of incipient fractures. Experience has taught that brittleness in steelusually increases with hardness, and the greater the brittleness the more the metal is susceptible to the formation of surface cracks or incipient fractures which eventually extend far I enough into the metal to cause completefailure" of the section affected. i

Our method and apparatus is applicable not only to gears, but to numerous other articles as hereinafter explained, such as splined shafts, reamers, drills, gun bores,'the wearing surface of pulverizing and crushing machines, friction this invention then has as its chief object the provision of an apparatus and method whereby the wearing surfaces of a gear may be hardened without detrimental changes affecting other parts of the gear. Another object is to provide a method and apparatus whereby the addendum, portions of all teeth may be hardened successively and uniformly. A further object is to provide a method whereby a portionof a gear after being hardenedmay be tempered to any desired degree. Numerous other objects will become apparent from the annexed drawings and the following description in which details of apparatus capable of producing improved results will be defined and new and advantageous steps in the procedure for obtaining such results will be described or suggested to those skilled in the art of heat treating. In the annexed drawings:

Fig. 1 is a longitudinal elevation showing oneform of our apparatus. I V, V

Fig. 2 is a plan'view ofthe apparatus shown inFig. 1.

Fig. 3 is an enlarged sectional view substantially at 3--3 of Fig. 1.

When it is required to harden the contacting surfaces of gears having relatively large teeth, particularly when the current available is not of the desired high frequency, apparatus of' the general form shown in the drawing of this application or some modification of it is employed. In this apparatus the gear issupportedon mandrel 5| which mandrel is carried'on' plate 52, this plate being slidable on top 53on the'main frame 54. Guide pins 55 engage a "groove 55' to control the direction of movement of the plate and screw 56 which is adjustable as to position serves to hold the plate in engagement with top 53 and limits the movement of this plate.

The gear 50 on its mandrel 5 l is held in correct heating position by conical plunger 63 which enters the space between two teeth of the gear. The angle of the conical end of the plunger is such as to be forced out of holding engagement by the application of considerable rotative force to the gear, the plunger being caused meme the next space between teeth by the spring 64.

With this apparatus the gear teeth are heated one at a time. Each tooth is brought into heating position such as that occupied by tooth 65 and is so located by plunger 63 engaging a toothon or near the opposite side of the gear, that the inductor comprising members 66 and 61 is positioned so that each of the members enters'a tooth space on opposite sides of the tooth. Each'of the inductor members is so formed as to correspond in shape with the side of ea'chof the-teeth and to lie in closely spaced relation thereto. The inductor members are connected as at 68 to permit current to flow in opposite directions in the two members, the current being supplied from a suitable source such as the transformer 69 and generator 10. The inductor members are insulatedly molded into and supported by carrier 15 and are thereby spaced from each other. The carrier is attached to top 53 of the main: frame. A cam, such as 80, engages the end of plate 52 to control the movement of this plate which movement is caused by spring 8! engaging an opposite end. The movement of the plate actuated by the spring and controlled by the cam permits the gear to move away from the inductor to bring a, tooth, which has already been heat treated, out of its position between the inductor members, thus permitting the gear to be rotated to a new position for heating another tooth. The cam is carried. on shaft: 82 which shaft. is supported in a part of frame 54 and is rotated at suitable speed by motor 83 connected thereto.

When cam 80 has been rotated far enough to letthe gear move, to bring the tooth out of the space between the inductor members; a further rotation of the shaft 82 and cam 80; lets the gear move back again toward the inductor. In. this return movement pawl. 81' engages gear 50, which serving as a ratchet, is rotated by this pawl, forcing plunger 63 outof its engagementinone tooth space. The: pawl rotates the gear far enough to permit the plunger to enter the next space. This brings a tooth adjacent to the one already heat treated into the space between the inductor members; To prevent the tooth" in entering the space between inductor members from interfering with these members, the limited rotative movement of the gear is, substantially completed before the entering movementoccurs. This is accomplished by having pawl 81 mounted on axially-moveable bar 89-. By means of cam 88 also carried on shaft 82 the pawl is given a limited movement parallel with that of plate 52 and in the same direction as that of the plate. This prevents the pawl from rotatin the gear while the gear and pawl are both moving in the same direction.

Since accurate timing of both heating and quenching is usually required, a. timerof suitable character such as discs 9| and'92 is so attached as to be rotated by shaft 82. A contactor 93 engaging disc 92 serves as means to operate solenoid 94 to close switch 95 for the required heating interval. Another contactor 91 engaging disc 9| operates to energize solenoid 98 to open quenching fluidv supply valve 99 at th correct time relative to'the termination of heating. Quenching isaccomplished by means of supply linelllll'which delivers quenchingfluid from valve 99 into space 96 from. which space it flows through passages lfll in theinductors as shown inFig. 5. The passages lll'l' are directed to deliver the quenching fluid against the heated tooth surfaces; The-quenching fluid line I is insulated from the inductor members by the carrier 15; This quenching fluid line together with inductor members 66 and 61, and the carrier '35 forma unit. This unit is adjustably and replaceably mounted on base 53, the screw 99a serving as means for holding this unit'in. such position asto heat the desired parts of toothBE. By changing to another unit means is provided for-hardening a tooth of different size and form of another gear.

Other forms may be employed embodying the features of our invention instead of the one herein explained, change being made as regards the means and the steps herein disclosed, provided the elements stated by any of the following claims or the equivalent of such stated elements be employed, or whether produced by our preferred method or by others embodying steps equivalent to those stated in the following claims.

We therefore particularly point out and distinctly claim as our invention:

1. In a method of heat treating surface zones of spaced metallic elements projecting generally radially from asubstantially cylindrical surface of an article, the steps comprising relatively moving an inductor and the article to carry the inductor along the surface of the article, stopping the relative movement when a part of the inductor is substantially opposite a space between adjacent elements, applying holding means to prevent. further relativemovement during a; prescribedtime interval, then radially, and relativelymoving the inductor and article toward each other to bringsaid part of the inductor into said space and into closely spaced relation. with a surface zone-of one of the projecting: elements, supplyin inducin current tothe inductor to heat the surfacezone'while holding the inductor in a fixed position relative to the article, then radially and relatively moving the inductor and the article. away. from each other to carrythe part of said inductor out of said space, and then moving the article relatively to the inductor to bring said part of the inductorsubstantially opposite to another space between elements of the article.

2. In a method of successively heat treating surface zones of a seriesof metallic elements projecting generally perpendicularly from the surface, of an article, the zones: of each element lying on substantially opposite sidesof the element, thesteps comprising providing an inductor in the form of a loop having generally opposite parallel sides, the said. sides having opposite inner faces formed to correspond generally in shape with the surface zones of the elements and being spaced from each other to provide space for one of said elements, relatively moving the inductor and the article to carry the inductor along the surface of the article and to brin an element into a position substantially opposite to the space between the inductor sides, applying means to fixedly position the article relative to said inductor, relatively movin the inductor and article toward each other to bring the element into the space between opposite sides of the inductor and to bring the zones into closely spaced relation with the sides of the inductor, supplying inducing current to the inductor to heat the surface zones while holding the element and inductor in substantially fixed relation, then relatively moving the inductor and article away from each other to carry the element out of the inductor and then relatively moving the inductor along the surface of the article to bring the space he.- tween'the inductor sides into alignment with another element of the article, and repeating the aforesaid steps until the surface zones of all of the elements have been heat treated;

3. In apparatus of the class described for heat treating successive projections on a cylindrical surface of a metallic article, an axial support for said article, means adapted to rotate the article on the support, an inductor adapted to liein closely spaced relation with a surface of a projection of the article when said article is in a predetermined position, said inductor comprising a conductor lying generally parallel with the axis of the support, means for intermittently supplying inducing current to the inductor, means for intermittently and relatively moving the inductor toward and away from the axis of the support, and means adapted to hold the article in a plurality of fixed predetermined positions to maintain the inductor always in a spaced predetermined relationship with the aforesaid projections when induced current is being supplied to said inductor.

4. In apparatus of the class described for heat treating successive projections On a cylindrical surface of a metallic article, an axial support for said article, means adapted to intermittently rotate the article on the support, an inductor adapted to lie in closely spaced relationship with a surface of a projection of the article, means adapted to releasably but fixedly hold the article in a plurality of fixed predetermined positions,

means for intermittently supplying inducing cur- 1 rent to the inductor, means for intermittently relatively moving the inductor toward and away from the axis of said support and means associated with all of said predetermined means mechanically interconnecting same for sequentially controlling the actuation thereof.

FRANCIS S. DENNEEN. WILLIAM C. DUNN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,878,458 Blanchet Sept. 20, 1932 2,067,549 Sykes Jan. 12, 1937 2,178,201 Dake Oct. 31, 1939 2,240,494 Denneen et al May 6, 1941 2,398,085 Denneen et a1. Apr. 9, 1946 FOREIGN PATENTS Number Country Date 416,928 Great Britain Sept. 17, 1934 445,425 Great Britain Apr. 8, 1936 Germany June 6, 1936 

